Most of our views of Mars are of a dry and desolate planet. Its tenuous atmosphere can create a global dust storm, but the planet is not weathered by the elements like Earth, so it's always fascinating getting new images that show just how active Mars was – and still is.
The European Space Agency’s orbiter, Mars Express, has photographed in detail a particular region of Mars known as the Nili Fossae. The region is known for being the largest known carbonate deposit on Mars and for the detection of methane. Methane could be a signature of biological processes going on underground, but it might also be unrelated to life.
The latest images released add to this fascinating area. Nili Fossae can be seen in incredible detail and the effect of not just wind, but also water and ice, are dramatically visible on the rocks. It's clear materials from higher altitude regions moved downhill, and the path the water took billions of years ago is still visible today. Chemical analysis of the terrain shows the presence of clay minerals, another clear hallmark of water.
The effects of the wind are also strikingly visible. The images from Mars Express show dark patches around the region. This is actually volcanic dust that has been transported and deposited by present-day winds into the depressions of Nili Fossae. The different colored sand is not an exclusive characteristic of Nili Fossae, however. Across the Red Planet, darker dune fields are evidence of the erosion still happening today on Mars.
Nili Fossae is characterized by many geological structures. There are rocky valleys, small hills, and several mesas, flat-top landforms. There are also several graben, ditches formed by the planet’s crusts bordered by faults.
The region is also at an interesting global boundary. Roughly speaking, Mars can be split into two. The northern hemisphere is smooth due to volcanic activity, while the southern hemisphere is full of more ancient regions and craters. Nili Fossae sits on this border, roughly 20 degrees north of the equator.
Mars Express was launched in 2003 and for the last 15 years has helped planetary scientists around the world understand the Red Planet better. The data collected by the orbiter has been crucial in building up the evidence for a once water-rich Mars.